recurrent threadworms

Discovered DS (2.5) had a nasty case of threadworms last Friday and treated with Ovex - symptoms seem to be back (disturbed sleep, itchy bottom) but can't give second dose within the fortnight. Does anyone know if there's anything else I can give him? I realise he's probably reinfected himself as although I washed all bedding, sleepwear etc, I forgot to do his bedtoys. Dur!Is this something I can get help for from a pharmacist or do I need to see a doc?